1. Field of the Invention
The present invention relates to a signal output board configured to output a drive signal for driving an electronic device, and an endoscope including the signal output board.
2. Description of the Related Art
In recent years, electronic endoscopes including a solid-state image pickup device, for example, a CCD, at a distal end of an insertion portion have widely been used in clinical sites. In an endoscope system including an electronic endoscope, a drive signal outputted from a signal output board is transmitted to a CCD provided at a distal end portion of an insertion portion via a cable, and a video signal from the CCD is transmitted to a camera control unit (hereinafter referred to as “CCU”) configured to perform signal processing, whereby an endoscopic image is displayed on a monitor.
Meanwhile, there is concern that EMI (electromagnetic interference) noise, which is electromagnetic noise leaked from an electronic circuit, negatively affects the other electronic systems in the surroundings. Here, since a CCD uses a drive signal with a rectangular wave of several tens of megahertz, harmonic components and high-frequency components of the drive signal tend to be generated as electromagnetic waves, that is, EMI noise. In order to prevent malfunctions due to EMI noise in the clinical sites where various kinds of electronic devices are arranged, EMI noise occurrence is strictly regulated by the Medical Device Directive (MDD).
Accordingly, for example, Japanese Patent Application Laid-Open Publication No. 2001-340289 discloses an electronic endoscope with an end of a shield material covering a cable, which connects a CCD and a signal output board, electrically connected to an insertion portion-sheathing metal member in order to suppress EMI noise from the cable.